Atlantic Ocean The Atlantic Ocean is the second-largest ocean, covering approximately one-fifth of the Earth's surface. The ocean's name, derived from Greek mythology, means the "Sea of Atlas ." The oldest known mention of this name is contained in Histories of Herodotus around 450 BC .
	Atlantic Puffin The Atlantic Puffin is a seabird in the auk family. It is a pelagic species that feeds primarily by diving for fish. Its most obvious characteristic is its brightly colored beak during the breeding seasons. Also known as the Common Puffin, it is the only puffin species which is found in the Atlantic Ocean.
	Atlantic sailfish The Atlantic sailfish is a species of sea water fish in family Istiophoridae of order Perciformes.
	Atlantic salmon Atlantic salmon is a fish species of the Salmonidae family found in the northern Atlantic Ocean and in rivers that flow into the Atlantic. The Atlantic salmon follows an "anadromous" fish migration pattern, in that it undergoes its greatest feeding and growth in salt water; but adults return to spawn in native fresh water streams where the eggs hatch and juveniles grow through several distinct stages.
	Atlantic tripletail The Atlantic tripletail, Lobotes surinamensis, is a warm water marine fish that can grow to 90 cm long and weigh 18 kg.
	Atlantis Atlantis is the name of an island first mentioned and described by the Ancient Greece philosopher Plato. According to him this island, lying "beyond the pillars of Hercules", was a naval power, having conquered many parts of western Europe and Africa. Soon after a failed invasion of Athens, Atlantis sank in the waves "in a single day and night of misfortune" due to a natural catastrophe which happened 9,000 years before Plato's time.
	Atlas An atlas is a collection of maps, traditionally bound into book form, but also found in multimedia formats. As well as geographic features and political boundaries, many often feature geopolitical, social, religious and economic statistics.
	Atlas Mountains The Atlas Mountains are a mountain range in northwest Africa extending about 2,400 km through Morocco, Algeria, and Tunisia, and including Rock of Gibraltar. The highest peak is Jbel Toubkal, with an elevation of 4,167 metre located at in southwestern Morocco.
	Atmometer The atmometer is a Measuring instrument invented by the Scotland mathematician and engineer Sir John Leslie. Atmometers also known as evaporimeters are used for measuring the rate of evaporation from a wet surface to the atmosphere. A simple set up may be made using a porous flat plate like object which can draw water from an easily measurable source via a wick of some sort.
	Atmosphere Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. The gases are attracted by the gravity of the body, and held fast if gravity is sufficient and the atmosphere's temperature is low. Some planets consist mainly of various gases, and thus have very deep atmospheres.
	Atmospheric electricity Atmospheric electricity is the regular diel variations of the Earth's Earth's atmosphere Electromagnetism electrical network. The Continent, the ionosphere, and the atmosphere is known as the global atmospheric electrical circuit.
	Atmospheric pressure Atmospheric pressure is the pressure above any area in the Earth's atmosphere caused by the weight of Earth's atmosphere. Standard atmospheric pressure is discussed in the next section. Air masses are affected by the general atmospheric pressure within the mass, creating areas of high pressure and low pressure .
	Atoll An atoll is a type of low, coral island found in Tropics oceans and consisting of a Coral reef usually surrounding an interior body of water called a lagoon or peninsula. Atolls generally mark the locations of subsidence extinct volcano islands; the shape of the atoll is determined by the initial coastline of the original volcanic island, and is maintained so long as coral growth is faster than subsidence, and is not disturbed by other factors.
	Atom In chemistry and physics, an atom is the smallest possible particle of a chemical element that retains its chemical properties. The word atom originally meant the smallest possible indivisible particle, but after the term came to have a specific meaning in science, atoms were found to be divisible and composed of smaller subatomic particles.
	Atom Smasher Atom Smasher is a fictional superhero in the DC Comics DC Universe.
	Atomic clock An atomic clock is a type of clock that uses an atomic resonance frequency standard to feed its counter. Early atomic clocks were masers with attached equipment. Today's best atomic frequency standards are based on more advanced physics involving cold atoms and atomic fountains.
	Atomic theory In chemistry and physics, atomic theory is a theory of the nature of matter. It states that all matter is composed of atoms. The philosophy background of the atomic theory is called atomism. The theory applies to the common phases of matter, namely solids, liquids and gases, as directly experienced on Earth.
	Atomism In natural philosophy, atomism is the theory that all the objects in the universe are composed of very small, indestructible elements - atoms. Or, stated in other words, all of reality is made of indivisible basic building blocks. The word atomism derives from the ancient Greek word atomos which means "that which cannot be cut into smaller pieces".
	Atrazine Atrazine, 2-chloro-4-(ethylamine)-6-(isopropylamine)-s-triazine, is a s-triazine-ring herbicide that is used globally to stop pre and post emergence broadleaf and grassy weeds in major crops. Atrazine binds to the plastoquinone-binding protein in photosystem II, inhibiting electron transport.
	Atreus In Greek mythology, King Atreus of Mycenae was the son of Pelops and Hippodamia and father of Agamemnon and Menelaus. Collectively, his descendants are known as Atrides. Atreus and his twin brother, Thyestes, were exiled by their father for having murdered their step-brother, Chrysippus in their desire for the throne of Olympia, Greece.
	Atrial fibrillation Atrial fibrillation is an abnormal heart rhythm which involves the two small, upper heart chambers. Heart rate in a normal heart begin after electricity generated in the atria by the sinoatrial node spreads through the heart and causes contraction of the heart muscle and pumping of blood.
	Atrial septal defect Atrial septal defects are a group of congenital heart diseases that enables communication between atria of the heart and may involve the interatrial septum. The inter-atrial septum is the tissue that separates the right atrium and left atrium atria from each other.
	Atriplex Atriplex is a plant genus of 100-200 species, known by the common names of saltbush and orache. The genus is quite variable and widely distributed. The genus includes many desert and seashore plants and halophytes, as well as plants of moist environments. Saltbushes are extremely tolerant of salt content in the ground: their name derives from the fact that they retain salt in their leaves, which makes them of great use in areas affected by soil salination.
	Atropa Atropa is a genus of plants in the nightshade family. Its best-known member is the deadly nightshade, Atropa belladonna. Its pharmacologically active ingredient is atropine. The genus is named for one of the Three Fates, the one which cut the life thread. In some older classifications, the mandrake is considered a species of the Atropa genus as Atropa mandragora.
	Atropine Atropine is a tropane alkaloid extracted from the deadly nightshade and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a hard drug with a wide variety of effects. Being potentially deadly, it derives its name from Atropos, one of the three Fates who, according to Greek mythology, chose how a person was to die.
	Attar Farid od-Din Attar was born in Nishapur, in the Iranian province of Khorasan and died in the same city. Some scholars believe he was killed during the raid and destruction of his city by the Mongol invaders. His tomb is in Neishapour. His death has quite a story: It's said that a mongol soldier found out who he was and was taking him to his officer when a man offered some money to buy Attar.
	Attic An attic is an area found directly below the roof of a building(also called a "garret", a "hayloft", a "sky parlor", and a "loft").As attics fill the space between the ceiling of the top floor of a building and most often a slanted roof, they are known for being awkwardly shaped spaces with exposed rafters and difficult-to-access corners.
	Attila the Hun Attila the Huhn was the final and most powerful List of Hunnic Rulers of the Huns. He reigned over what was then Europe's largest empire, from 434 until his death. His empire stretched from Germany and the Netherlands to the Ural river and from the Danube to Poland and Estonia.
	Attractor In dynamical systems, an attractor is a set to which the system evolves after a long enough time. For the set to be an attractor, trajectories that get close enough to the attractor must remain close even if slightly disturbed. Geometrically, an attractor can be a point, a curve, a manifold, or even a complicated set with fractal structures known as a strange attractor.
	Aubergine The aubergine , also known as the eggplant or the brinjal is a Solanum plant bearing a fruit of the same name, commonly used as a vegetable in cooking. It is closely related to the tomato and potato and is native to southern India and Sri Lanka. It is an annual plant growing 40 - 150 cm tall , often spine , with large, coarsely lobed leaf 10-20 cm long and 5-10 cm broad.
	Auckland The Auckland Metropolitan Area, or Greater Auckland, in the North Island of New Zealand, is the largest New Zealand urban area in New Zealand. With over 1.2 million people it has almost a third of the country's population. It is a conurbation, made up of Auckland City , North Shore, New Zealand, and the urban parts of Waitakere and Manukau cities, along with Papakura and some nearby urban parts of Rodney District and Franklin Districts
	Auction An auction is the Process of trade things by offering them up for bid, taking bids, and then selling the item to the highest bidder. Auctioning can be traced as far back as 500 B.C. In economic theory, an auction is a method for determining the value of a commodity that has an undetermined or variable price.
	Aucuba Aucuba is a genus of three to ten species of flowering plants, now placed in the family Garryaceae, although formerly usually classed in the Aucubaceae or Cornaceae. Aucuba species are native to eastern Asia, from the eastern Himalaya east to Japan. They are evergreen shrubs or small trees 2-13 m tall, similar in appearance to the laurels of the genus Laurus, having glossy, leathery leaves, and are sometimes mistakenly called laurels.
	Audacity Audacity is a free software, Open Source, cross platform digital audio editor. The source code for Audacity is released under the GNU General Public License. The graphical user interface for the editor has been produced using the wxWidgets Library.
	Audio amplifier An audio amplifier is an electronic amplifier that works with audio frequencies. It is the final stage in the audio playback chain and its purpose is to amplify the electrical audio signal from its preceding stage to a level that can drive the loudspeaker. The preceding stages are low power audio amplifiers which perform tasks like preamplifier, equalization, Tone control circuits, mixing console, etc or audio sources like record players, CD player
	Auditorium An auditorium is the area within a theater, concert hall or other performance space where the audience is located in order to hear and watch the performance. For movie theaters the number of auditoriums is also expressed as the number of screens. The term is taken from the Greek language auditorium which was a series of semi-circular seating shelves in the Theatre of Ancient Greece, divided by broad 'belts', called diazomata, with eleven rows of seats between each.
	Audubon's Warbler The Audubon's Warbler, Dendroica coronata auduboni, is a small New World warbler. This passerine bird was long known to be closely related to its eastern counterpart, the Myrtle Warbler, and at various times the two forms have been classed as separate species or grouped as the Yellow-rumped Warbler, Dendroica coronata.
	Auger An auger is a device for moving material or liquid by means of a rotating helical flighting. The material is moved along the axis of rotation. A drill bit uses this mechanism to remove shavings from a hole being drilled. For some uses the helical flighting is enclosed in a tube, for other uses the flighting is not encased.
	Augite Augite is a mineral described chemically as(Mg, Fe, Al)(Al, Si)2O6 or calcium sodium magnesium iron aluminium silicate. The crystals are monoclinic and prismatic. Augite has two prominent prismatic cleavages, meeting at angles near 90.
	Augur The Augur was a priest and official in ancient Rome. His main role was to take auspices: interpreting the will of the gods by studying the flight of the birds , known as "taking the auspices." The ceremony and function of the augur was central to any major undertaking in Roman society--public or private--including matters of war, commerce, and religion.
	August August is the eighth month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. August begins with the sun in the sign of Leo and ends in the sign of Virgo . Astronomically speaking, the sun begins in the constellation of Cancer and ends in the constellation of Leo .
	August Strindberg Johan August Strindberg was a Sweden writer, playwright, and painter. He is ranked among Sweden's most important authors. Strindberg is known as one of the fathers of modern theatre. His work falls into two major literary movements, Naturalism and Expressionism.
	Auguste Comte Auguste Comte was a French positivism thinker and came up with the term of sociology to name the new science made by Claude Henri de Rouvroy, Comte de Saint-Simon.
	Auguste Rodin Auguste Rodin was a France Sculpture, often given a pivotal role in the history of modern sculpture, as both excelling at and rebelling from the Beaux-Arts architecture tradition. His unique, virtuoso ability to organize a complex, turbulent, deeply pocketed surface set him apart from the figure sculpture traditions before and since his time.
	Augustine of Hippo Aurelius Augustinus, Augustine of Hippo, or Saint Augustine was one of the most important figures in the development of Western Christianity. In Roman Catholic Church, he is a saint and pre-eminent Doctor of the Church, and the patron of the Augustinians.
	Augustinians The Augustinians, named after Saint Augustine of Hippo, are several Roman Catholic Church monastic orders and congregations of both men and women living according to a guide to religious life known as the Augustinians#The Augustinian Rule.
	Augustus Augustus , known as Gaius Julius Caesar Octavianus for the period of his life prior to 27 BC, was the first and among the most important of the Roman Emperors. Although he preserved the outward form of the Roman Republic, he ruled as an Autocracy for more than 40 years, and his rule is the dividing line between the Republic and the Roman Empire.
	Auk Auks are birds of the family Alcidae in the order Charadriiformes. They are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits. Nevertheless they are not related to the penguins at all, but considered by some to be a product of moderate convergent evolution.
	Aum Aum is the most sacred syllable in Hinduism, symbolizing the infinite Brahman and the entire Universe. This syllable is sometimes called the "Udgitha" or "pranava mantra", because it is considered to be the primal sound, and because most mantras begin with it. It first appeared prominently in the Vedic religion.
	Aurochs The aurochs is a very large, extinct type of cattle, originally prevalent in Europe. The word aurochs is both singular and plural; alternative plural forms are aurochsen or urus. The animal's original scientific name, Bos primigenius, translated the German language term Auerochse or Urochs, literally "primeval ox", or "proto-ox".
	Austen Austen may refer to: * Jane Austen, an English novelist. * Austen Tayshus, an Australian comedian known for Australiana.
	Austenite Austenite is a metallic, non-magnetic solid solution of iron and an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1333 F; other alloys of steel have different eutectoid temperatures. It is named after Sir William Chandler Roberts-Austen.
	Australasia Australasia is a term variably used to describe a region of Oceania namely Australia, New Zealand, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes. He derived it from the Latin language for "south of Asia" and differentiated the area from Polynesia and the southeast Pacific; it is also distinct from Micronesia.
	Australia Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the world's smallest continent and a number of islands in the Southern Ocean, Indian Ocean, and Pacific Oceans.
	Australian Alps The Australian Alps are the highest mountain ranges of mainland Australia. They are located in south-eastern Australia, straddling far southern New South Wales and eastern Victoria, Australia. The Alps contain the Australian mainland's only peaks exceeding 2,000 metres Australian Height Datum and it is only here that snow occurs regularly.
	Australian cockroach The Australian cockroach is a large species of cockroach, winged, and growing to a length of 1 1/4"-1 3/8". It is brown in colour. It is very similar in appearance to the American cockroach and may be mistaken for it easily. However, it is a bit smaller than the American cockroach, has a yellow margin on the thorax, and yellow streaks at its sides as the wing base.
	Australian dollar The Australian dollar has been, since 1966, the currency of the Commonwealth of Australia, including Christmas Island, Cocos Islands, and Norfolk Island, as well as the independent Pacific Islandss of Kiribati, Nauru and Tuvalu. It is normally abbreviated with the dollar sign $.
	Australian Magpie The Australian Magpie is a medium-sized black and white bird, closely related to the butcherbirds and currawongs. Early European settlers named it for its black and white coloration, similar to the familiar European Magpie, which is a more distant relative.
	Australian Sea Lion The Australian Sea Lion is a species of sea lion that breeds only on the south coast of Australia. Today there are about 12,000 Australian Sea Lions following the introduction of the Australian National Parks and Wildlife Act of 1972 which prohibited a harvest that began in earnest as soon as Europeans colonised the continent.
	Australian Terrier image = Australian_terrier.jpg | image_caption = 250px | name = Australian Terrier | country = Australia | nickname = Aussie | fcigroup = 3 | fcisection = 2 | fcinum = 008 | fcistd = akcgroup = Terrier | akcstd = ankcgroup = Group 2 - Terrier | ankcstd = ckcgroup = Group 4 - Terriers | ckcstd = kcukgroup = Terriers
	Australopithecus The gracile australopithecines are a group of extinct hominids that are closely related to Homo .
	Australopithecus afarensis Australopithecus afarensis is a hominid which lived between 3.9 to 3 million years ago. In common with the younger Australopithecus africanus, A. afarensis was slenderly built, or gracile. It is widely believed that A. afarensis is the ancestor of the genus Homo, which includes our own species, Homo sapiens.
	Australopithecus africanus Australopithecus africanus was an early Hominidae, an australopithecine, who lived between 3.3 and 2.4 million years ago in the Pliocene. In common with the older Australopithecus afarensis, A. africanus was slenderly built, or gracile, and was thought to have been a direct ancestor of modern humans.
	Austria Austria is a landlocked country in central Central Europe. It borders Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the west. Its capital city is Vienna.
	Austria-Hungary Austria-Hungary, also known as the Austro-Hungarian Empire, Dual Monarchy or K.u.k. Monarchy or Dual State, was a personal union state in Central Europe from 1867 to 1918, dissolved at the end of World War I. The dual monarchy was the successor to the Austrian Empire on the same territory, originating in the Ausgleich between the ruling Habsburg dynasty and the Hungarians.
	Austrian schilling The Schilling was the currency of Austria until 1999, and the circulating currency until 2002. The euro was introduced at a fixed parity of 1 = 13.7603 Schilling to replace it. The "Schilling" was divided into 100 Groschen.
	Austrians This article is about the Austrians as an ethnic group. For information on citizens or nationals of Austria, see demographics of Austria; for information on speakers of the Austrian dialect of German, see Austrian-German language. Austrians are defined as an ethnic group, in the sense of sharing a common Austrian culture, speaking the German language as a First language and being of Austria Kinship and descent.
	Austro-Asiatic languages The Austro-Asiatic languages are a large language family of Southeast Asia, and also scattered throughout India and Bangladesh. The name comes from the Latin word for "south" and the Greek language name of Asia, hence "South Asia". Among these languages, only Vietnamese language, Khmer language, and Mon language have a long recorded history, and only Vietnamese and Khmer have official status .
	Austronesian languages The Austronesian languages belongs to a language family widely dispersed throughout the islands of Maritime Southeast Asia and the Pacific, with a few members spoken on continental Asia. It is on par with Indo-European languages and Uralic languages as one of the best developed and most secure language family proposals.
	Autism Autism is classified as a Neural development disorder that manifests itself in markedly abnormal social interaction, communication ability, patterns of interests, and patterns of behavior. Although the specific Causes of autism is unknown, many researchers suspect that autism results from genetically mediated vulnerabilities to environmental triggers.